LISP Support for Disjoint RLOC Domains

The Locator/ID
Separation Protocol (LISP) implements a “level of indirection” that enables a
new IP routing architecture. LISP separates IP addresses into two namespaces:
Endpoint Identifiers (EIDs), which are assigned to end-hosts, and Routing
Locators (RLOCs), which are assigned to devices that make up the global routing
system.

The LISP Support for
Disjoint RLOC Domains feature enables LISP-to-LISP communication between LISP
sites that are connected to different RLOC spaces but have no connectivity to
each other. One example of disjointed RLOC space is that of between the
IPv4 Internet and IPv6 Internet. When one LISP site has IPv4-only RLOC
connectivity and the second site has IPv6-only RLOC connectivity, these sites
can still communicate via LISP using the LISP Support for Disjoint RLOC Domains
feature.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for
LISP Support for Disjoint RLOC Domains

Map servers and
re-encapsulating tunnel routers (RTRs) must have connectivity to all locator
spaces that are being joined.

Information About
LISP Support for Disjoint RLOC Domains

LISP Support for
Disjoint RLOC Domains Overview

The fundamental
principal of any network is that routing and reachability must exist between
all devices that make up the total network system. There are many network
systems, public and private, for which internetwork connectivity is not
directly available. A few examples include:

IPv4 Internet and IPv6
Internet.

An IPv4 Multiprotocol
Label Switching (MPLS) VPN from service provider A and an IPv4 MPLS VPN from
service provider B.

An IPv4 MPLS VPN from
service provider A and IPv4 Internet.

When some sites
within a network connect to one routing domain and other sites connect to another routing domain, a gateway function must be provided to
facilitate connectivity between these disjointed routing domains. In
traditional routing architectures, providing connectivity between disjointed
routing domains can be quite complex.

The inherent
property of Locator/ID Separation Protocol (LISP), which separates IP addresses
into two namespaces, endpoint identifiers (EIDs) and routing locators (RLOCs), also gives it the ability to connect disjointed RLOC domains. The LISP Support
for Disjoint RLOC Domains feature provides simplified configuration mechanisms
that enable this capability. The key components are new control plane
configuration options on the LISP map server, and a functionality called
re-encapsulating tunnel router (RTR), which provides data plane connectivity
between disjointed locator spaces.

LISP
Map Server

The key concept
in the LISP Support for Disjoint RLOC Domains feature is the recognition that
the LISP Mapping System has full knowledge of all LISP sites. When a LISP site
registers with a map server, the registration message not only provides
information about the EID space that the site is authoritative for, but it also
provides information about its own RLOCs.

The LISP Support
for Disjoint RLOC Domains feature provides new configuration options to define
within the map server the routing locator scopes that LISP sites can
connect to. Once defined, the map server automatically determines whether individual sites have common or disjoint locator
connectivity between themselves. The map server then uses this knowledge when
handling Map-Request messages to determine how to inform LISP sites to
communicate with each other. Map-Request messages contain both source and
destination EID information. When a map server receives a Map-Request message,
it compares the RLOCs associated with the source EID and destination EID
contained with the Map-Request message against the configured locator scopes.

If the ingress tunnel
router (ITR) (source EID) and egress tunnel router (ETR) (destination EID)
share at least one RLOC in a common locator scope, the map server forwards the
Map-Request message to the ETR as normal. In this case, the ETR is capable of
generating a Map-Reply message that is sent back to the ITR since it has
reachability across (at least one) common locator space.

If the ITR (source EID)
and ETR (destination EID) do not share at least one RLOC in a common locator
scope, the map server sends a proxy Map-Reply message to the ITR that includes
a list of RTRs that are capable of connecting the disjointed locator space
between the ITR and ETR.

If the RLOCs associated
with the ITR (source EID) and ETR (destination EID) do not match any configured
locator scopes, the map server forwards the Map-Request message to the ETR as
normal. In this case, the RLOCs are assumed to be reachable via routing, even
though they are not defined in any locator scope configuration.

LISP data plane
packets flow directly between sites when the sites share locator space. An RTR
is used to connect LISP data plane packets when locator spaces between the
sites are disjointed.

LISP
RTR

A
re-encapsulating tunnel router (RTR) provides data plane communications support
for LISP-to-LISP traffic between LISP sites that do not share common locator
space. Functionally, an RTR takes in LISP encapsulated packets from an ITR in
one locator scope, decapsulates them, does a map-cache lookup, and then
re-encapsulates them to an ETR in another locator scope. The following are
important considerations for an RTR:

The RTR itself must have
RLOCs in all locator scopes that are being joined.

An RTR sends Map-Request
messages to populate its own map cache. As a Map-Request message contains an
ITR RLOC field that is populated with one or more entries corresponding to the
locators of the device sending the Map-Request message, the RTR in this case,
the locator set configuration is also required on the RTR to define its
locators. This enables the map server to correctly receive Map-Requests from
the RTR to assess locator scope connectivity.

An RTR performs functions
similar to a proxy ingress tunnel router (PITR) and proxy egress tunnel router
(PETR), therefore these features must be enabled on the RTR.

Specifies the
interface type and number and enters interface configuration mode.

Step 4

ip addressip-address mask

Example:

Device(config-if)# ip address 10.10.10.4 255.255.255.0

Configures an
IPv4 address for the interface.

Step 5

ipv6 addressipv6-address/ipv6-prefix

Example:

Device(config-if)# ipv6 address 2001:DB8:0:ABCD::1/64

Configures an
IPv6 address for the interface.

Step 6

interfacetypenumber

Example:

Device(config)# interface ethernet0/0

Specifies the
interface type and number and enters interface configuration mode.

Step 7

ip addressip-address mask

Example:

Device(config-if)# ip address 10.0.4.1 255.255.255.252

Configures an
IPv4 address for the interface.

Step 8

router lisp

Example:

Device(config-if)# router lisp

Enters
LISP configuration mode.

Step 9

locator-setlocator-set-name

Example:

Device(config-router-lisp)# locator-set R4

Specifies a
locator set and enters LISP locator set configuration mode.

Step 10

ipv4-addressprioritypriority-locatorweightlocator-weight

Example:

Device(config-router-lisp-locator-set)# 10.0.4.1 priority 1 weight 1

Configures
the LISP locator set. The LISP locator set is the set of addresses the
first-hop router uses when communicating with the gateway xTR. You can configure
each IPv4 locator address by creating a locator entry with assigned priority and
weight.

Configures
the LISP locator set. The LISP locator set is the set of addresses the
first-hop router uses when communicating with the gateway xTR. You can configure
each IPv6 locator address by creating a locator entry with assigned priority and
weight.

10.Repeat Step
7 to Step 9 to specify and configure another locator set.

11.locator-scopename

12.rtr-locator-setlocator-set-name

13.rloc-prefixipv4-rloc-prefix

14.exit

15.Repeat Step
11 to Step 14 to specify and configure another locator scope.

16.sitesite-name

17.authentication-keypassword

18.eid-prefixipv4-eid-prefix

19.eid-prefixipv6-eid-prefix

20.exit

21.Repeat Step
16 to Step 20 to configure another LISP site on the map server.

22.ipv4
map-server

23.ipv6
map-server

24.ipv4
map-resolver

25.ipv6
map-resolver

26.exit

27.ip routeprefix mask ip-address

28.ipv6 routeipv6-prefix/prefix-length ipv6-address

29.end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Device> enable

Enables
privileged EXEC mode.

Enter your password if
prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global
configuration mode.

Step 3

interfacetypenumber

Example:

Device(config)# interface ethernet0/0

Specifies the
interface type and number and enters interface configuration mode.

Step 4

ip addressip-address mask

Example:

Device(config-if)# ip address 10.0.2.1 255.255.255.252

Configures an
IPv4 address for the interface.

Step 5

ipv6 addressipv6-address/ipv6-prefix

Example:

Device(config-if)# ipv6 address 2001:DB8:1::1/64

Configures an
IPv6 address for the interface.

Step 6

router lisp

Example:

Device(config-if)# router lisp

Enters
LISP configuration mode.

Step 7

locator-setlocator-set-name

Example:

Device(config-router-lisp)# locator-set rtr-set1

Specifies a
locator set and enters LISP locator set configuration mode.

Step 8

ipv4-addressprioritypriority-locatorweightlocator-weight

Example:

Device(config-router-lisp-locator-set)# 10.0.3.1 priority 1 weight 1

Configures
the LISP locator set. The LISP locator set is the set of addresses the
first-hop router uses when communicating with the gateway xTR. You can configure
each locator address by creating a locator entry with assigned priority and
weight.

Specifies
the IPv4 source address to be used in LISP IPv4 Map-Request messages. The ITR
RLOCs configured under Steps 7 through 10, and Step 11 take precedence.
However, this step (16) is still required.

Step 17

ipv4
map-cache-limitcache-limit

Example:

Device(config-router-lisp)# ipv4 map-cache-limit 100000

(Optional) Specifies
maximum number of IPv4 LISP map cache entries allowed to be stored on the
router. The valid range is from 0 to 100000.

Additional References for LISP Support for Disjoint RLOC Domains

Related
Documents

Technical
Assistance

Description

Link

The Cisco Support and Documentation website provides online
resources to download documentation, software, and tools. Use these resources
to install and configure the software and to troubleshoot and resolve technical
issues with Cisco products and technologies. Access to most tools on the Cisco
Support and Documentation website requires a Cisco.com user ID and password.

Feature
Information for LISP Support for Disjoint RLOC Domains

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Feature
Name

Release

Feature
Information

LISP
Support for Disjoint RLOC Domains

15.4(1)T

The LISP
Support for Disjoint RLOC domains feature enables LISP-to-LISP communications
between LISP sites that are connected to different RLOC spaces but have no
connectivity to each other.